linux-kernel - Re: Linux 3.3-rc4

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Date:	Tue, 21 Feb 2012 12:52:39 +0800
From:	Ian Kent <raven@...maw.net>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	David Miller <davem@...emloft.net>, thomas@...3r.de,
	linux-kernel@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: Linux 3.3-rc4

On Mon, 2012-02-20 at 20:17 -0800, Linus Torvalds wrote:
> On Mon, Feb 20, 2012 at 8:02 PM, Ian Kent <raven@...maw.net> wrote:
> >
> > It doesn't but changing it for exiting binaries will break existing
> > binaries that use a workaround.
> 
> What existing binaries?

My bad, autofs for one, but obviously when running in compat mode.
And any other user space users, such as the auto_dir package, but I
don't know if that is maintained any more.

> 
> > I'm proposing this because the systemd folks were happy to do it this
> > way. But if you would like any other existing user space users to change
> > to using a correctly sized packet then, yes, it isn't what you want to
> > happen.
> 
> Existing binaries *do* use the correct size packet - it's the correct
> size for native x86-32!
> 
> It's our x86-64 compat layer that is wrong. It's a clear bug. Nothing else.
> 
> We don't start making up new interfaces because we have clear bugs: we
> fix the damn bugs.
> 
> How could you even sanely do "workarounds"? A x86-32 binary shouldn't
> even be able to *tell* that the kernel is 64-bit. And if it does that
> somehow, we should fix that too!

Sure, not an acceptable excuse I know, but it was too late when I
realized my mistake.

So, as you say, let's fix the bug.

autofs is by far the biggest user and I can manage the change for it and
I can at least post to the auto_dir list (if it still exists) and Thomas
can feedback to the systemd folks.

Then there is the question of how it should be done.

I think the patch attached to your original post needs a little work if
that is to be used. Correct me if I'm wrong but AFAICT there are more
architectures that use 8-byte alignment than just x86-64, such as alpha,
ia64 and ppc64 and I believe they may also be used in a compat mode.

Is there a better way to do this change, anyone?

Ian

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